I'm confused over some weird behaviour my clown loach has been demonstrating over the last few weeks... He's verging on the 20cm mark now, and seems to think he's a lot smaller. There are some stories I could tell of, including him getting himself stuck in a shipwreck ornament, and swimming through a line of about 30 plants clumsily enough to uproot all that he passed through.
Just yesterday, I'd taken off the whole lid of the tank to clean it, basically. I heard a 'splash', turned my head, and saw he'd jumped out the water, and fallen down the back of the tank, the dozey mare :

As it's only about an inch away from the wall, and the back-less cupboard underneath is filled with spare tanks, plants, gravel, food and what have you, I had a major panic trying to get him back in the water. Although he seemed quite quiet after that, he did try and take on my red-tailed shark this morning (with the light on - he never used to even come out with the light on) and got a bit bumped around in the process.
Other than that, he's been okay - and it's only really the last two or three weeks he's been acting up. Jumping out the tank was like... well, the point where I really started to worry. He might have just panicked after bumping into something; he's like that sometimes, but never leaves the bottom third-ish of the tank.
Should I worry? Should I not?
Anyone else had this happen to them?
